1. Field of the Invention
The present invention relates to an on-vehicle power generation controller which is mounted on a vehicle and is driven by an internal combustion engine. More specifically, the present invention relates to an on-vehicle power generation controller capable of controlling power generation by employing a plurality of generators having the same structures.
2. Description of the Related Art
Among conventional on-vehicle power generation controllers, an on-vehicle power generation controller has been equipped with a controller for controlling turning on and off of a field current so as to adjust a generated voltage to a predetermined voltage. Also, while a plurality of the above-mentioned on-vehicle power generation controllers are employed, there have been known systems in which a plurality of generators are driven at the same time by a single engine so as to simultaneously generate electric power (refer to, for instance, JP 3061700 B and JP 04-38131 A).
FIG. 8 is a circuit diagram showing a generally available on-vehicle power generation controller. First of all, a description is made of operations of the on-vehicle power generation controller equipped with the below-mentioned controller with reference to FIG. 8. That is, the controller controls turning on and off of a field current so as to adjust a generated voltage to a predetermined voltage, and to control power generating operations of a generator. The on-vehicle power generation controller shown in FIG. 8 includes a generator 1, a rectifier 2, and a controller 3, and in addition, is externally equipped with a battery 4 and a key switch 5.
In such a case that an engine (not shown) is started, when the key switch 5 is closed (turned ON), a current is supplied from the battery 4 via the key switch 5 to a terminal “R” of the controller 3. As a result, a current is supplied via a resistor 304 and a diode 305 to a base terminal (base electrode) of a transistor 309, so the transistor 309 is brought into a conductive state.
Then, because a base current of a transistor 310 flows through a resistor 308, the transistor 310 is brought into a conductive state, and thus, a current is supplied via a resistor 311 to a zener diode 312. Since this current flows, a power supply “A” having a constant voltage may be constructed, while the constant voltage constitutes a power supply voltage of the controller 3.
Then, a comparator 317 is brought into an operable state by the power supply “A”. The comparator 317 compares a voltage of an input terminal (+) corresponding to a constant reference voltage value with a voltage of another input terminal (−) to control a field current on-off control transistor 301. The above-mentioned reference voltage value as to the input terminal (+) is obtained by dividing the constant voltage of the power supply “A” by resistors 315 and 316. The voltage of another input terminal (−) is obtained in such a manner that the voltage of the battery 4 is monitored via an external sensing terminal “S”, and the monitored-voltage is sub-divided by resistors 313 and 314.
Since the generator 1 has not yet generated electric power until the engine is started, a voltage of the input terminal (−) corresponding to the divided voltage of the battery 4 becomes lower than the voltage of the input terminal (+), so a “Hi” signal (namely, signal having high level) is outputted from the comparator 317. As a result, the field current on-off control transistor 301 is brought into a conductive state, so a field current flows through a magnetic field coil 102, and thus, the generator 1 is brought into an electric power generatable condition.
Next, when the engine is started, the power generating operation by the generator 1 is commenced, so a voltage at an output terminal 201 of the rectifier 2 is increased. Since the output voltage of the rectifier 2 is increased, the battery 4 is charged, so the voltage of the battery 4 is increased. As a result, if both the voltage at the sensing terminal “S” of the battery 4 and the voltage of the input terminal (−) corresponding to the divided voltage are increased higher than the voltage of the input terminal (+) corresponding to the reference voltage, then an output signal of the comparator 317 becomes a “Lo” output (namely, output signal having low level), so this “Lo” output may cut off the transistor 301. Since the transistor 301 is operated by such a cut off mode, the field current which has flown through the magnetic field coil 102 is decreased, so the output voltage of the generator 1 is lowered.
When the output voltage of the generator 1 is lowered and the voltage of the input terminal (−) of the comparator 317 becomes lower than the voltage of the input terminal (+) thereof, the comparator 317 again outputs the “Hi” signal, so the transistor 301 is brought into the conductive state. Since a series of the above-mentioned operation is repeatedly carried out, the output voltage of the generator 1 is adjusted and controlled to become the constant voltage value.
Also, the controller 3 is equipped with a terminal “M” for outputting a field current on-off control signal, by which signals can be outputted outside the controller 3 when the transistor 301 is conductive. As a result, the signals synchronized with the operations of the transistor 301 can be outputted from the terminal “M”, so the “Hi” signal is outputted from the terminal “M” when the transistor 301 is conductive, whereas the “Lo” signal is outputted from the terminal “M” when the transistor 301 is cut off.
In such a case where even maximum output power derived from one generator 1 is not sufficient for all of electric loads required by an engine, there are some possibilities that the plurality of generators 1 having the same structures may be operated with respect to a single engine. FIG. 9 is a structural diagram showing a conventional on-vehicle power generation controller under such a condition that the plurality of generators 1 are operated with respect to a single engine. In FIG. 9, two on-vehicle power generation controllers containing two generators having the same structures are exemplified, while a first on-vehicle power generation controller is indicated as “G1” and a second on-vehicle power generation controller is indicated as “G2.”
When the plurality of generators 1 constructed in the same manners are operated at the same time by a single engine so as to simultaneously generate electric power, conductive states of the transistors 301 provided in the respective controllers 3 are not identical to each other due to various sorts of factors, for instance, variations in adjusted voltages of the controllers 3 caused by manufacturing variations, differences of wiring lines between a battery and the power generation controllers, which are produced when the power generation controllers are mounted on the single engine.
FIG. 10 is a diagram showing operation waveforms at respective units employed in controllers in such a case where a plurality of generators having the same structures are driven at the same time by a single engine so as to simultaneously generate electric power. More concretely, the operation waveforms show states at the terminal “R”, the transistor 301, and the terminal “M” employed in the controller 3 as to each of the two on-vehicle power generation controllers “G1” and “G2” previously shown in FIG. 9.
As shown in FIG. 10, due to the various factors, the conductive states of the transistors 301 provided in the respective controllers 3 are not identical to each other. As a result, there is such a problem that because the power generating conditions of the two generators are not equal to each other, the voltages become unstable.
Also, for instance, there is a problem that, in the case where such a condition that an electric power generating condition of only one generator is increased among a plurality of on-vehicle power generation controllers is continued, a lifetime of the one generator becomes short, as compared with lifetimes of other generators. Further, there is another problem that, in connection with the fluctuation of the lifetimes, longer times and higher costs are required for maintenance and the like, as compared with those of the conventional system.
As solving ideas for the above-mentioned problems, there have been proposed certain structures in which unbalanced conditions of the respective generators are to be adjusted (refer to, for instance, JP 3061700 B and JP 04-38131 A).
However, the conventional technologies have the below-mentioned problems.
That is, in the conventional technologies disclosed in JP 3061700 B and JP 04-38131 A, the structures of the on-vehicle power generation controllers are complex. As a result, the conventional technologies have such a problem that the costs as to the on-vehicle power generation controllers themselves are increased, or the structures as to the plurality of the generators are not made identical to each other.